Optical fibre trial shows “groundbreaking” speeds possible

Nokia Bell Labs, Deutsche Telekom T-Labs and Technical University of Munich achieve speeds of 1Tb per second in optical technology trial

In jointly conducted research of optical systems, Nokia Bell Labs, Deutsche Telekom T-Labs and the Technical University of Munich achieved a 1 terabit per second transmission rate over optical fibre.

The group achieved strong transmission capacity and spectral efficiency in an optical communications field trial with a new modulation technique. The research, called a “breakthrough” by the participants, could extend the capability of optical networks to meet surging data traffic demands, they claimed.

The demonstration shows that the flexibility and performance of optical networks can be maximised when adjustable transmission rates are dynamically adapted to channel conditions and traffic demands.

As part of the Safe and Secure European Routing (SASER) project, the experiment over a deployed optical fibre network of Deutsche Telekom achieved a net 1Tb transmission rate. This is close to the theoretical maximum information transfer rate of that channel and thus approaching the Shannon Limit of the fibre link. The Shannon Limit was discovered in 1948 by Claude Shannon, Bell Labs pioneer and the “father of information theory.”

The trial of the novel modulation approach, known as Probabilistic Constellation Shaping (PCS), uses quadrature amplitude modulation (QAM) formats to achieve higher transmission capacity over a given channel to significantly improve the spectral efficiency of optical communications.

PCS modifies the probability with which constellation points – the alphabet of the transmission – are used. Traditionally, all constellation points are used with the same frequency. PCS cleverly uses constellation points with high amplitude less frequently than those with lesser amplitude to transmit signals that, on average, are more resilient to noise and other impairments. This allows the transmission rate to be tailored to ideally fit the transmission channel, delivering up to 30% greater reach.

The research is a key milestone in proving PCS could be used in the future to extend optical communication technologies, said the companies.

It was 50 years ago when optical fibre was introduced. With the promise of 5G wireless technology on the horizon, optical transport systems today continue to evolve to help telecommunications operators and enterprises meet network data traffic growing at a cumulative annual rate of up to 100%. PCS is now part of this evolution by enabling increases in optical fibre flexibility and performance that can move data traffic faster and over greater distances without increasing the optical network complexity.

Gerhard Kramer, Professor, Technical University of Munich, said : “Information theory is the mathematics of digital technology, and during the Claude E. Shannon centenary year 2016 it is thrilling to see his ideas continue to transform industries and society. Probabilistic constellation shaping, an idea that won a Bell Labs Prize, directly applies Shannon’s principles and lets fiber optic systems transmit data faster, further, and with unparalleled flexibility. The success of the close collaboration with Nokia Bell Labs, who further developed the technology, and Deutsche Telekom T-Labs, who tested it under real conditions, is satisfying confirmation that TUM Engineering is a label of outstanding quality, and that TUM teaching gives our students the intellectual tools to compete, succeed and lead globally.”

While Marcus Weldon, president Nokia Bell Labs & Nokia CTO, said: “Future optical networks not only need to support orders of magnitude higher capacity, but also the ability to dynamically adapt to channel conditions and traffic demand. Probabilistic Constellation Shaping offers great benefits to service providers and enterprises by enabling optical networks to operate closer to the Shannon Limit to support massive data centre interconnectivity and provide the flexibility and performance required for modern networking in the digital era.”

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